net: dsa: add master helper to look up slaves

The DSA tagging code does not need to know about the DSA architecture,
it only needs to return the slave device corresponding to the source
port index (and eventually the source device index for cascade-capable
switches) parsed from the frame received on the master device.

For this purpose, provide an inline dsa_master_get_slave helper which
validates the device and port indexes and look up the slave device.

This makes the tagging rcv functions more concise and robust, and also
makes dsa_get_cpu_port obsolete.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 14 deletions

diff --git a/net/dsa/tag_qca.c b/net/dsa/tag_qca.c
index 1d4c707..8d33d9e 100644
--- a/net/dsa/tag_qca.c
+++ b/net/dsa/tag_qca.c
@@ -65,9 +65,6 @@ static struct sk_buff *qca_tag_xmit(struct sk_buff *skb, struct net_device *dev)
 static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 				   struct packet_type *pt)
 {
-	struct dsa_switch_tree *dst = dev->dsa_ptr;
-	struct dsa_port *cpu_dp = dsa_get_cpu_port(dst);
-	struct dsa_switch *ds;
 	u8 ver;
 	int port;
 	__be16 *phdr, hdr;
@@ -92,20 +89,12 @@ static struct sk_buff *qca_tag_rcv(struct sk_buff *skb, struct net_device *dev,
 	memmove(skb->data - ETH_HLEN, skb->data - ETH_HLEN - QCA_HDR_LEN,
 		ETH_HLEN - QCA_HDR_LEN);
 
-	/* This protocol doesn't support cascading multiple switches so it's
-	 * safe to assume the switch is first in the tree
-	 */
-	ds = cpu_dp->ds;
-	if (!ds)
-		return NULL;
-
 	/* Get source port information */
 	port = (hdr & QCA_HDR_RECV_SOURCE_PORT_MASK);
-	if (!ds->ports[port].netdev)
-		return NULL;
 
-	/* Update skb & forward the frame accordingly */
-	skb->dev = ds->ports[port].netdev;
+	skb->dev = dsa_master_get_slave(dev, 0, port);
+	if (!skb->dev)
+		return NULL;
 
 	return skb;
 }